Millions of birds migrate every year to escape winter, but spending time in a warmer climate does not save them energy, according to new research. Using miniaturized loggers implanted in wild blackbirds, scientists recorded detailed measurements of heart rate and body temperature from birds every 30 minutes from fall to the following spring. The data offer unprecedented insights into the true energetic costs of migrant and resident strategies and reveal a previously unknown mechanism used by migrants to save energy prior migration.
